I think you could do both, without overloading kind 0. You'd publish a product-specific metadata event, and a fallback profile that includes a link to somewhere you can view the full listing. I don't think that would mess anything up, and it would get you the fallback you're looking for. 

 Fallback profile, mhm, could works.
But are you still talking about a keypair for every product? 

 Yeah, and while for products I still don't really see a big benefit, it's a reasonable design choice.